martin



Oct. 22, 1929. H. MARTIN 1,732,275

RES I STANCE ELEMENT Filed March 8, 1921 3 Sheets-Sheet 1 Oct. 22, 1929. MARTIN 1,732,275

.nssrsuncx; ELEMENT Filed March 8. 1921 3 Sheets-Sheet 2 mrmwmi;

Oct. 22, 1929. H. MARTIN RESISTANCE ELEMENT 3 Sheets-Sheet 3 Filed March 8. 1921 Patented Oct. 2 2, 1929 HAROLD MARTIN, OF SOUTHSEA, ENGLAND RESISTANCE ELEMENT Application filed March 8,;192i, Serial Not ;950,666, and in Great Britain March 11, 1920,

This invention relates to improvements'in manometersof the kind in"whi ch' a U-tube containing mercury' or other conducting liquid is connected to the higher and lower pres- 6 sure regions of a pressure difference device such a Venturi or Pitot tube. H

The primary object of the present invention is to provide an electrically operated manometer which can be used for direct reading and/or recording, for remote control purposes.

In order that the invention may be'clearly understood and readily carried into'efiect it is hereinafter described-With reference .to the accompanying drawings, in which Figure 1 is. a side elevation illustrating'the general arrangement of'a resistancefliia idm eter constructed according'to this invention, one of the legs of the U-tube bei'n'g shown in section in order to illustrate the internal construction;

Figure 2 is an inverted plan view'lof the disc at the lower end of one of the resistance elements; I Figure 3 isa to'p planview of the disc at the upper end of the resistance element;

Figure 4 is a detail sectional view of an oil separator adapted for use on each of the limbs of the manometer;

Figure 5 is a diagram illustrating a simple arrangement of the electrical. connections, and A i Figure 6 isa diagram illustrating these connections arranged in a -,way which has been found in practice-to give good working results.

As shownin Figures Land 2 and according to this invention, I arrange within each, of the conducting legs a a of the U tube, which are preferably of iron, an insulated frame made by means of four iron rods 6 spaced apart by means of ebonite end pieces 9 g as shown in Figures 1, 2 and 3. Upon these iron rods are threaded a number of, preferably, porcelain or glass beads b which are so disposed that a length of iron or other suitable wire 0 which is wound by being laid in the grooves formed by the rounded ends of adjacent beads becomes a regular helix of approximately 60 square instead of circular shape. One end minal d fixed in the lower end-plategflwhile the upper end is connected to screw or termi; nal d fixed into a brass terminal plate/which is connected through a phosphor bronze spring 6 to the main terminal plate f which is completely insulated as indicated in igure'l from both the cover plate 8 and the case of'the instrument a. The frame and wirejarefsup ported upon or immediately above an ebonite or other suitable insulated distance piece 1' which is channeled to permit of theifree' passage of the mercury,.g.- A.flangedfebonite insulating sleeve t is als'oprovi d e' d for iise, more particularly in cases where there is as water or other electrolyte abovefthemercury in the legs of the manometen fflhe instru ment shown, designed for use j ntie'i."" lii'gh fluid pressure, has suitable rubber jointing and insulating rings at the upper 'end of each (0 leg between the cover .9, the terminal plate}, the insulating sleeve 25 and thecase a. The metal studs which are screwed into the flanged ends of the le s of the manometer; case are also insulated by means of ebonite other suitable sleeves as shown. The pressure difference which it is desired to measure is transmitted to the mercury'in the manometer by means of the vertical cocks and Ts shown at the top of the instrument'which are c'onnectso ed into the cover plates, holes being provided in the terminal plates'below' them a 's necessary. Horizontal cocks areforiequaliz} ing, testing or draining as necessary when using the instrument. 'Anebonite or other suitable core I) is arranged through the centite of each coil and between the ends plates 9 9' simply in order to reduce the quantityand weight of mercury necessary to operate theinstrument. Normally with no pressure dif; 9 ference the mercury gis so arranged'asfto leave an equal portion of the resistance'wire of each coil 0 exposed so that the two coilso a can be connected up together with the casing to a suitable source of E. M. F. as as uitable form of electric balance system working on say the potentiometer or \Vheatstone bridge principle, or some modification thereof, as indicated diagrammatically in Figs. 5 and Thus, any relative variation in the' lev'el 1 of this wire 0 is madefa st toa screw or'terof the mercury or other conducting liquid g in the legs a a of the'U-tube will upset the balance of the system and cause a pointer or other indicating or recording arm to be deflected proportionately. Conveniently the indicating or recording part of the manometer may comprise a pair of soft needles k k as in the working diagram show'n in Figure 6 each pivotally arranged at the centre of two concentric coils i j, i 7' having-their; axes at right angles to one another. The

position taken up by the needles is will there fore depend upon the ratio of the currents which "are passed through the'two pangf coils, this ratiovarying as the mercury rises or falls in the U-tube under the influence of the fluid ,pressure-difl'erence device employed. Though a single soft iron needle in conjunction with one pair of ratio coils can beuscd, as indicated in Fig. 5, wherein'i and indicate the two coils, the advantage of using two needles with two similar pairs of coils, the outer coil of one pair being in series with the inner coil of the other pair, as shown in Fig. 6, is that all errors due to inequalities in the mner and outer concentric coils are thereby eliminated. The two such soft iron needles It would be mechanically linked or connected to a common pointer or recording arm I 'as shown. In one convenient method of arranging the circuits the free insulated ends of the resistance wires 0, c on the cores in the U -tube would be connected one to the inner coilj and the other to the inner coil 7' the other ends of said inner coils being connected to the outer coils 2' and z" respectively. The-ends of the coils i i would also be connected together and to the case m at the middle of the U-tube or to the mercury inside where a glass or non-conducting U-tube is employed. The source of E. M. F. ii would be connected across the ends Of the resistance wires 0 c at the top of the legs of the U-tube.

Primarily to ensure good insulation but also in order to prevent corrosion due to electrolytic action, I may, as shown in Fig. 4, arrange oil n on top of the mercury in the legs a, water 7) providing asuitable seal or trap 0 for the water p in connection with each of the pressure connections if using the manometer for steam or water measurement. 7

It will be seen from the foregoing description that the improved electrically operated manometer can be used for a large variety of purposes such as for measuring the flow of steam or water or other fluids, for ascertaining the water level of steam generators, or the level of petrol or other liquids in containers. The measurement. of the flow of fluids may be done by means of measuring the pressure difference produced by the flow of the fluid across an orifice, Pitot tube, Venturi tube or the like or by measuring the height of a column of Water or other liquid flowing over a weir or notch. It can also be used to give any desired form of alarm upon predetermined limits being reached. Also for boiler work such a manometer could be made to operate in conjunction with one or more indicators to indicate flow of steam, or level of water at different places say at one point convenient for the stoke'r and the other in' the pow'e'rstation superintendents oflicc.

"Obviously also any suitable form of indicating instnumentcim be used with such an electrically operated manometer.

5 Inor-di'n ary cases it is proposed to use a low voltagegt to 8 volt, secondary battery for thecurrent' 'supplyto the apparatus. The latter, however, can obviously be operated from anf'o'rdinary lighting circuit, if necessary were suitable resistance such as a lamp inser'ted so'th'at there is only a comparatively low-.volt ag'e' across the manometer itself. There is no difficulty in making "the type of indicator shown into a recording instrument, though a rather more powerful movement would, in" this case, be desirable. The arrangements shown in the drawings provide an indicating instrument with a central'zero, and with a maximum deflection through an angle of 45 degrees. The lengths of the resistance coils and mercury columns are norfinally arranged to suit the maximum pressure difference to be measured, but'if measuring lip to'any reduced maximum pressure differur the sensitivity of the indicator can be increased by raising the level of themercury in the legs of them'anometer, providing that.

the'minimum pressure difler'ence which has to be measured is within the reduced range of the manometer resulting from'ra'ising the mercury level.

Itwill also beseen that if it .is desired to avoid electrical apparatus and the consequentflow of current, inside the manometer, the movement of the spindle, arm, pointer, etc., of any apparatus designed to measure the depth, movement,'velocity or flow of a fluid which is normally arrangedto operate indicating or measuring gear, may be alternatively or additionally, arranged to move a contact relative to a resistance, such movable contact being equivalent to the mer cury or other liquid in'the above mentioned manometer arran ement and thereby providing the means or deflecting the indicator proportionately to its movement which may be electrically connected up and located in any convenient position.

Obviously, if desired, the movement of the mercury in such a manometermay be measured by means of one coil in one leg only, a suitable indicator being an ordinary ammeter calibrated to operate in series with the resistance coil of the manometer, from a supply, .the voltage of which, however, must be quite constant. An arrangement like this, in addition to errors introduced by variations in supply voltage, is also liable to errors due to resistance of connecting leads, and other parts. With the two coil manometer, in conjunction with the indicator previously described, after once calibrating the indicator to read the diflerence in heights of the columns of mercury in the two legs, correct readings should always be obtained, and it will be found that the instrument is independent of variations of supply voltage, resistance of leads and other parts. While the resistance coils can be regularly wound upon any suitable insulated core or frame, the frame previously described has been found to overcome difliculties arising out of the tendencies of the coils to retain mercury between them and their supports, and of the supports themselves to become permanently coated with a film of mercury, thereby varying the resistance of the exposed portion of the coil and consequently producing errors.

If desired the apparatus described may also be used to measure inclination in which case the manometer casing is fixed to the apparatus, such as a gun, whose inclination or elevation it is desired to measure, or a ship the roll of which it is desired to record. The movement of the manometer legs relative to the mercury columns (which in this case remain level), is indicated or recorded and is a measure of the inclination of the apparatus to which the manometer is attached. When used for this purpose certain parts such as the pressure connections and oil seals, would not be required, nor would any oil or other liquid be required above the mercury in the legs.

What I claim is 1. As an article of manufacture, a resistance member for manometers and the like comprising in combination four rods united to insulating end pieces and extending parallel to each other; a series of non-conducting beads threaded on each of the rods so as to be contiguous to each other and form a continuous series extending for the entire length of said rod, said beads being confined between the insulating end pieces; and a resistance wire wound on the frame provided by the four iron rods, being laid in the grooves provided by the beads and providing a helixlike resistance element of approximately rectangular cross section.

2. In a manometer, a resistance member having wound thereon a resistance wire, said resistance member adapted to be partially immersed in the mercury of the manometer; and a spring at the upper end of the resistance member, said spring being electrically connected with a terminal plate and also being electrically connected with the resistance wire of the corresponding resistance member.

In testimony whereof I have hereunto signed my name.

HAROLD MARTIN. 

